Air conditioning apparatus



May 5, @310 F. F. BAHNSQN l w AIR CONDITIONING APPARATUS Filed Oct. 13, 1928 7 Sheets-Sheet 1 May 5, 3931., F. F. BAHNSQN 19869491979 AIR CONDITIONING APPARATUS Filed 0013. 13, 1928' 7 Sheets-Sheet 2 grvuvntoiz May 5, 193110 F. F. BAHNSON 1,8494%79 AIR CONDITIONING APPARATUS 7 Sheets-Sheet 5 Filed Oct. 13, 1928 y 9 3 F. F. BAHNSN wmaw AIR CONDITIONING APPARATUS Filed 001;. 13, 1928 '7 Sheets-Sheet 4 A? :55 a: r1 26 F. F. BAHNSON AIR CONDITIONING APPARATUS Filed Oct. 13, 1928 7 Sheets-Sheet 5 May 5, 1931,, F. F. BAHNSN 7 19849493979 AIR CONDITIONING APPARATUS Filed Oct. 15, 1928 7 Sheets-Sheet 6 May 5, 1933, F. F. BAHNSON AIR CONDITIONING APPARATUS wmww Filed Oct. 13. 1928 7 Sheets-Sheet 7 Patented May 5, 1931 STATES FREDERIC F. BAHNSON, OF WINSTON-SALEM, NORTH CAROLINA, ASSIGNOR TO THE BAHNSON COMPANY, OF WINSTON-SALEM, NORTH CAROLINA, A CORPORATION OF NORTH CAROLINA AIR CONDITIONING APPARATUS Application filed October 13, 1928. Serial No. 312,287.

This invention relates broadly to air-conditioning apparatus, including humidifying apparatus, and control devices for regulating the operation of the humidifying apiparatus so that various conditions of hum1 and temperature of the air within certain confines may be appropriately employed as instrumentalities in determining the conditioning effect produced by the humidifying apparatus. c

In my Patents, No. 1,439,217 granted December 19, 1922, and No. 1,544,418. granted June 30, 1925, are disclosed devices for automatically controlling the feed of water to a i humidifying apparatus of the type in which water is projected into the surrounding air in pulverized or atomized condition by means of a current of air produced by a fan. This control apparatus is designed for operation primarily in the immediate vicinity of the humidifier and is preferably mounted 011 the humidifier itself. Thus, in an installation including a plurality of humidifiers provided with control devicesof this type, each humidifier operates in accordance with the humidity conditions immediately surrounding it.

In my Patent No. 1,657,362 granted January 24, 1928, I have disclosed an installation of a plurality of humidifiers provided with control devices of the type described and have added to such installation means whereby the rate at which water is fed to such humidifiers may be varied in response to variations in the temperature of the space in which the air conditioning is effected by the humidifiers. In such an installation it will be apparent that the operation of the humidifiers is controlled not only by the conditions of humidity immediately surrounding them but also by the general room temperature.

I have found that, in installations such as that last described, conditions arise which cannot be adequately met by the instrumentalities provided. For example, in such an installation in a factory or mill, it is quite possible for a humidifier or humidifiers in one portion of a room (where there may be stored hygroscopic materials) to operate for such a length of time as to raisethe humidity in that portion of the room to the point of actual dampness or wetness, with attendant injury to stock and machinery.

One of the objects of the presentinvention is to provide a master control or master controls for all of the humidifiers in a particular installation, whereby the operation of all of such humidifiers may be governed in response to conditions of humidity surrounding such master control or controls, it being understood that the individual control devices and the temperature-responsive control device previously referred to may also be included as elements in the installation.

Another object of the invention is to provide appropriate apparatus for effecting the master control referred to.

The invention consists, broadly, in the combination with an installation of air conditioning apparatus including a plurality of humidifiers, of master control apparatus for governing the operation of all of the humidifiers in the installation in response to gen eral humidity conditions in a room as reflected by the conditions in a chosen location in which the master control apparatus is placed; and the invention consists further in the particular construction of such master control means, as I will proceed now to explain and finally claim.

In the accompanying drawings illustrating the invention, in the several figures of which like parts are similarly designated.

Fig. 1 is a diagrammatic view of a typical installation of air-conditioning apparatus embodying the present invention,

Fig. 2 is a condensed rear elevation of the master control device, the casing members thereof being shown in section,

Fig. 3 is a section taken on line 3-3 of Fig. 2,

Figs. 4 and 4m show, in complete elevation, the upper and lower portions, respectively of the master control device, the casings enclosing and protecting the mechanisms thereof being shown in section,

Fig. 5 is a sectional elevation taken on line 5-5 of Fig. 2,

Fig. 6 is a sectional elevation taken on line 6-6 of Fig. 2,

Fig. 7 is a detail plan view of the suspension member of the humidity responsive element,

Fig. 8 is a wiring diagram showing the control mechanism operated by the master control device.

'Referring now to Fig. 1, wherein a typical installation of air-conditioning apparatus according to my invention is shown, it will be seen that I employ a number of humidifier units 1 preferably of the type disclosed in my Patent No. 1,544,418 hereinbefore referred to, each of which includes a humidity-responsive control device 2 preferably of the type disclosed in my Patent No. 1,439,217, also referred to. These units 1 are so relativel arranged and directed (see arrows) as to urnish moisture to the air in such quantities and directions as will provide the most desirable atmospheric condi- "dnnn thg'unii'c 1 it: nnnnnnfprl through the valve of its control device, with connected with one or the other of two branch pipes 4, 4' which lead to a water main 5. 6 indicates the temperature responsive device or thermostat of my Patent No. 1,657,362, and 7, 7 are the two ressure varying devices controlled by the evice 6 for varying the pressure of the water fed to the units 1 in response to the influence of temperature changes upon the device 6.

For the purpose of controlling the ma tion of all humidifier units connecte respectively, with the branch pipes 4 and 4',

I provide master control apparatus indicated at 8 and 8, located in such positions as to be subject to the effects of air of more or less stable humidity content. Each master control apparatus, as will be hereinafter fully explained, is adapted to operate a switch which controls an electric circuit 9, 9' including a relay 10, 10 and the motor and control devices 11,11 of an automatic valve 12, 12. As will be seen, these valves 12 and 12. are so placed in the branch pipes 4, 4 as to control the supply of water thereto from the main 5. Thus when the humidity content of the air surrounding the master control apparatus 8, 8, in their selected 10- cations where atmospheric conditions tend more or less testability, rises above a predetermined percentage for which the control apparatus is adjusted, the apparatus will function to effect the closing of the valves 12, 12 and thus cut off the supply of water to the units 1. Conversely, when the humidity content falls below the predetermined ercentage, the valves 12, 12' will be opened.

and o erated switches, indicated diagrammatica y at 13 and 13', are provided for manually controlling the operation of the valves 12 and 12.

casin By this arrangement of devices and their adjuncts it will be apparent that all conditions of operation of the humidifier units 1 may be effectively controlled. 7

The master control apparatus will now be described in detail, reference being had to Figs. 2 to 7, inclusive.

A bed plate 14 provides a bearing member for all of the operative parts of the control apparatus and may be provided with a suitable bracket, as indicated at 15, (Fig. 5) by which the apparatus may be fastened to a column, wall, or other suitable support. This bed plate 14 lies normally in a horizontal plane and has extending upwardly and downwardly from it rigid rods 16 and 17, respectively.

The rods 16 carry at their upper ends a plate 18 spaced relatively to the bed plate 14 and forming a guide for a foraminous member 19 of wire cloth, as shown, perforated metal or other suitable The th nclosed space above the gr 0 bed plate 14 forms a chamber in which the humidity responsive element of the apparatus is arranged and protected.

The rods 17 carry at their lower ends a plate 20. The plates 14 and .20 are provided with shoulders 21 and 22, respectively, between which is clamped a casing member 23 which may be of any suitable material, such as sheet metal, glass or celluloid. Vithin the space thus enclosed is mounted the electric switch mechanism.

The humidity responsive element includes a ribbon or stri of hygroscopic material, preferably a strip of paper 24, carried in sinusoidal arrangement upon a plurality of rods or rollers 25 and 25 mounted in upper and lower bearing members 26 and 27 re spectively. These bearing members are composed of appropriately lar plates 28 and 28 respectively, held in spaced relation so as to provide for free rotation of the rollers 25 and 25, by means of connector members 29 and 29 and spacer rods 30 and 30, respectively.

The upper bearing member 26 is supported by means of a metallic strap 31 from a suspension member 32 (see Figs. 3 and4) comprising a pair of spaced .plates ,33 between which is rigidly carried a block 34. This block 34 is provided with a square opening 35 through which extends a bar 36 to which the upper end of the strap 31 is fixed. The bar 36 is made adjustable relatively to the suspension member 32 by means of an adjusting screw 37 threaded into the barand bearing against the top of an abutment member 38 which seats against the block 34 and is recessed, as shown in Fig. 3', to receive the upper end of the'bar 36. The block 34 is notched at 39 to rovide a clamping piece 40 against which ears the end of a set screw 41 threaded into the block 34.

shaped pairs of simiclamping screw 45.

By this arrangement, when an appropriate tension has been put upon the member 24 by manipulation of the adjusting screw 37, the bar 36 may be fixed in adjusted position by forcing the piece 40 against the bar 36 by means of the set screw 41. As will be seen (Fig. 3) when the set screw 41 has been adjusted it may be sealed in position so as to prevent tampering by means of a sealing plug 42 of metal, wax or other suitable material. By these means a preliminary relatively permanent adjustment of the humidity responsive means may be obtained.

Alteration of this adjustment within certain limits is obtained by means of the following mechanism :The suspension member 32 is pivoted at one end to the plate 18 by means of a metallic hinge strip or leaf 43 suitably clamped to the block 34 as shown, and fixed to the plate 18 by a lug 44 and The opposite end of member 32 bears against a vertically arranged rod 46 screw-threaded into a bearing block 47 as shown at 48. This rod has clamped upon it an operating lever 49 provided with a handle 50 and index 51, which latter registers with a fixed scale 52 (Fig, 5). Turning .of the lever 49 by means of its handle 50 will result in a raising or lowering of the rod 46 and a concomitant raising or lowering of the free end of the member 32 upon its pivot.

Thus with the adjustment of the tension upon the member 24 previously fixed by means of the screw 37 and its adjuncts so that the device will operate in response to a certain predetermined humidity condition, a fine alteration of such adjustment within predetermined limits may be made by appropriate manipulation of the lever 49.

It will be understood that varying conditions of humidity in the atmosphere effective to vary the tension of the hygroscopic member 24, will be reflected by said member in its operation of the electric switch mechanism, hereinbefore referred to, which is utilized for opening and closing a master water valve 12-12 which controls the supply of water to the humidifier units 1.

The switch mechanism includes a pair of adjustable stationary contact points 53 and 54 and a movable contact member comprising an arm 55 provided with contact points 56 and 57 complemental to the fixed points 53 and 54, respectively. The fixed points 53 and 54 are mounted in bars 58 and 59, respectively, secured upon standards 60 affixed to the plate 14. Insulating blocks 61 are interposed between the bars 53 and 59 and the standards 60. The movable arm 55 is hinged by a metallic strap or leaf 62 to the plate 14, and is provided with an adjustable weight 63 which normally tends to cause the contact 54 and 57 to engage.

Fixed by means of a metallic hinge strap or leaf 65 to a suitable bracket 64 carried by the standards 60 is a lever 66 carrying at its upper extremity a bearing member 67 normally tending to press against the upper portion of the arm 55 under the influence of an adjustable weight 68 mounted on a supplemental lever extension 69 of the lever 66.

To the lever extension 69 is attached one end of a metallic strap 70, the other end of which is aflixed to the connector member 29 of bearing member 27. By this arrangement it will be seen that when the member 24 contracts under the influence of relatively low humidity conditions, the lever extension 69 will be raised and the parts will assume the positions shown in Figs. 3, 4 and 4a. But, when the member 24 expands under the influence of relatively high humidity conditions, the lever extension 69 will lower, the bearing member 67 will press against and move the movable arm 55, the contacts 54 and 57 will separate, and the contacts 53 and 56 will engage.

In order that a very quick and non-chattering engagement of the contacts of arm 55 and the respective fixed contacts may be had, I provide means for positively completing the final movement of arm 55 When the hygroscopic element has carried it past its dead-center position between the two fixed contacts. These means comprise a spring toggle arrangement including a toggle link 71 having its ends provided with needle points which find seats in sockets 72 and '73. carried, respectively, by the end of the arm 55 and by a flat spring 74 mounted upon the ends of the standards 60. Adjusting screws 75 are provided for varying the tension upon the spring 74 and hence the pressure which tends to break the toggle system formed by link 71 and arm 55.

Three binding posts, H, L and C, are carried by the plate 14. The post H is connected by wire 76 with the contact 53, the post L is connected by wire 77 with contact 54 and the post C is connected through the arm 55 to contacts 56 and 57. The movable arm 55 is connected with the binding post C by means of a member 78 formed preferably of a ribbon or strip of sliver. This type of connector is used for the reason that it is so soft and non-resilient as to offer no appreciable resistance to the movement of the arm 55. The various circuits controlled in response to the movements of the arm 55 through connections with the binding posts will be fully set forth in connection with the detailed description of Fig. 8.

It will be apparent from aninspection of Figs. 4 and 4a, which, when taken together, show the complete apparatus, that there is a relatively great'length of hygroscopic material 24 presented to the effect of the humidity of the surrounding atmosphere, with a commensurate multiplication, in its conchanges is relatively infinitesimal, and hence desirable where extreme accuracy and sensitiveness are essential, I have devised an arrangement and form of apparatus of such nature that the effect of such contraction or extension is so magnified as to produce de- 'sired, useful, mechanical functions.

The electrically operated water valves 12, 12 are of a. well-known type and may be purchased complete and ready for installation. But, in order that theoperation of such a valve in the installation of my invention may be readily understood, I have shown its essential elementsdiagrammatically in connection with the wiring diagram of Fig. 8. The valve comprises a globe or other suitable body'80 having a seat 81 and a cooperating disc 82 provided with a stem 83 and adapted to open against pressure. The stem 83 extends into the path of movement of a cam 84 carried on the shaft .85 of a motor 86. Also carried on the shaft 85 of the motor 86 is a cam 87 which cooperates with follower members 88 and 89 mounted on the legs 90 and 91, respectively, of a spring contact and conductor member fixed upon a suitable insulating base 92. The legs 90 and 91 carry contact points 93 and 94, respectively, which are arranged to engage similar points 95 and 96, respectively, carried by conductor bars 97 and 98, both of which are fixed upon the base 92. The cam 87 is of such peripheral contour that every time it rotates through 180 it will open or close the electrical contact between the points 93 and 95 or 94 and 96, but,.as will be apparent one or the other set of these contacts is always in engagement. I

The spring contactand conductor member is connected with one pole of the motor 86 by a wire 99. The other pole of the motor is directly connected with one side 100 of the power line by a wire 101.

The bars 97 and 98 are connected respec-' tively with points 102 and 103 of the handoperated switch 13 or 13'. A point 104 of this switch is connected with the other side 105 of the line. Another point 106 of this switch is connected through a wire 107 with the relay 10 or 10.

The rela 10 or 10 includes three switches, a, and 0, all of which are connected with and simultaneously operated by the core d of a solenoid e in such manner that when the switches a and b are open the switch 0 will be closed and vice versa.

The solenoid e is connected through a' re sistance f and wirev 108 with the side 105 of the line, and it is also connected, through wire 109 with the post H of the master control 8 or 8'. Its circuit is completed throii h wires 110, 111 and 112 with post C of t e master control.

The post L of the master control is connected through wire 113 with the contact of switch a, and through wire '114 with the side 100 of the line.

A spring 115 is provided for returning the core d of the solenoid and the switches a, b and 0 to normal position, as shown, when the solenoid is deenergized.

The hand operated switch has a turn button 116 which carries three contact bars 117, 118 and 119.

When the pointer of the turn button points in the direction shown, the bar 117 closes a circuit through the points 104 and 106 and the apparatus is ready for automatic operation. When it points downward a circuit is closed by bar 118 through points 104 and 102. When it points to the left a circuit is closed by bar 119 through points 104 and 103. When it points u ward all circuits are open and power is o The operation of the master control apparatus is as follows, it being understood that the various parts of the master control accessories are in the positions shown in Fig. 8.

When the relative humidity drops below the desired point for which the device 8 or 8' is adjusted, the hygroscopic member 24 will contract and will pull up on strap and lever extension 69, thus moving member 67 of lever 66 away from arm 55 and permitting the arm to move'under the influence of weight 63 in a direction to cause engagement of contacts 54 and 57 This movement will be made practically instantaneous by the action of the toggle lever 71. When contacts 54 and 57 engage, contact is established between C and L. This closes a circuit through the coil of the solenoid 0 through wires 100, 114, 120, 112, 111, 110, resistance f and wires 108 and 105. The coil thus magnetized throws the switches a, b and c and the circuits through a and b are closed, while the circuit through c is opened. The circuit through a merely shorts the contact points 54 and 57 between C and L so that the relay switch will be held in even thou h these points should separate. The switci b closes a circuit through wire 100, motor 86, wire 99, leg 90, points 93 and 95, bar 97, and wires 121 and 122, thus energizing the motor and causing it to turn until the high point of the cam 87 passes by follower 88 and permits the circuit to be broken between points 93 and 95. At the same time cam 84 will have turned and despressed the stem 83 of the valve to open it and permit water to flow to the humidifier units.

Obviously, when the cam 87 has turned sufiiciently to permit disengagement of points 93 and 95 it will have established engagement between points 94 and 96.

When the relative humidity reaches the point for which the control apparatus is adjusted, the hygroscopic member will have become sufliciently distended to permit the weighted lever extension 69 to so drop that member 67 will press against arm 55 and impart sufiicient movement to it to separate contacts 54: and 57 and permit engagement of contacts 53 and 56 under the influence of toggle lever 71 to thus establish contact between H and C. This contact shorts the coil of the solenoid 6 so that very little current passes through it, and its magnetic attraction for the core 03 is so weakened that spring 115 retracts the core thus closing switch 0 and opening switches a and Z). The current now flows through wires 100 and 101, motor 86, wire 99, leg 91, contact points 94 and 96, bar 98, wires 123 and 124, switch 0, wire 107, member 117 and wire 105.

Thus the motor 86 is again energized and turns the cam 87 until the engagement between points 94 and 96 is again broken and that between points 93 and 95 reestablished. At the same time the cam 84 is so rotated as to permit seatingof valve disc 82 under the influence of its spring and the pressure of the water acting against it, and the supply of water to the humidifier units is cut ofi'.

These circuits maybe thus automatically established and broken indefinitely so long as the hand switch 13 or 13 remains set at automatic, and humidity conditions efi'ective upon the master control ap aratus demand. However, by so adjusting t e switch that a circuit is closed through points 104 and 102 the valve 12 or 12 will be held open, and by so adjusting it that a circuit is closed through points 104 and 103 the valve will be permitted to remain closed, as will be apparent when the complete circuits thus established through the motor are traced.

Arcing at the several contacts is reduced to a minimum as the toggle system formed by contact arm 55, link 71 and spring 7 4 provides a rapid and positive engagement of the hygroscopicall controlled contacts 53, 57 and 54, 58. C attering can take place when these sets of contacts open but arcingwill not occur as there is no flow of current in the circuits when these sets of contacts open, the respective circuits having been previously opened by the motor operated contacts 93, 95 and 9%, 96,respect1vely.

It is to be noted that the hygroscopic strip 24 is always under tension and thereby is continuously operative to shift the position of lever 56 in accordance with the length of the strip. Although the device is hi hly sensitive to humidity changes, it is of an exceedingly rugged construction which will not necessitate constant attention. The use of heavy lever arms and strap hinges revents changes in the mechanical multipfication of the system from temperature variations, overloading of the mechanism or changes in frictional resistance. By employing a long strip passing over rollers, a relativel high operating force may be obtained rom a fabricated strip of hygroscopic material which is so thin that its response to changes in humidity is practically instantaneous. The unit stress to which the strip 24 is subjected should be kept low in order that the strip may not be stressed beyond its elastic limit.

As indicative of the relatively low stress to which the thin strip is subjected, the following data is given with reference to the particular hygroscopic strip and control device illustrated in the drawings. The lever system exerts a pull of about twelve ounces upon the strap and this weight or pull is not materially afiected by movement of the levers due to changes in the length of the paper strip. As shown in the drawings, this weight is divided between twenty-three strands to reduce the load on each strand to the order of substantially less than one ounce. As the breaking strength of a single strand of the particular paper was about six pounds, it will be evident that the load per strand is only a very small fraction of the load which it could carry. By subject ing the paper to a stress which is but a small fraction of its ultimate strength and elastic limit, the hygroscopic strip will not be stretched or otherwise changed by the load to which it is subjected.

The invention is not limited to the use of a multi-strand strip in which the load does not exceed a particular value with respect to the ultimate strength and/or elastic limit, but does contemplate the use of a thin same curve as that which represents change of length for varying amounts of absorbed moisture.

It is to be noted that an adjustment of the hygrometric control for temperature variations may be efl ected automatically by a proper choice of materials for the supporting rods 16, 17 and the adjusting rod 46'. When rod 46 has the same coefiicient of expansion as the supporting rods, the adustment of the control does not vary with temperature changes. By forming adjusting rod 46 of material having a relatively higher coeflicient of expansion, increases invidmg for higher humidity at higher tem peratures.

The connecting stra and lower supporting rods 17 may e used in a similar manner to effect a predetermined temperature adjustment of the humidity control. The particular adjustment may be positive, negative or zero depending upon the relative coefficients of expansion of strap 70 and rods 17 i. e., when strap 70 expands at a lower rate than rods 17, a positive adjustment resulting in higher humidity at increasing temperatures is obtained, and when the rates of expansion are equal the temperature adjustment is zero. It is to be understood that the master control apparatus per se is not limited in its application to the control of a water valve, but is susceptible of use in various installations where the throwing of an electric switch is to be effected in response to changes in the humidity of the atmosphere to which the apparatus is subjected.

My copending application Ser. No. 498,- 857, filed Nov. 28, 1930, describes and claims the hygroscopic control element per se, and methods of manufacturing the same, and my co ending application Ser. No. 477,925, filed ug. 26, 1930 describes and claims a hygroscopic control device which differs in some respects from that disclosed in the accompanying drawin Various changes, lfoth in the general installation and in the construction and operation of the master control apparatus are deemed to be within the spirit of the invention and the scope of the following claims.

I claim: I

1. In air conditioning apparatus, the combination with a plurality of humidifying units and means for supplying water thereto, each of said units provided with a humidity-responsivelmember for controlling its individual water supply, and means responsive to temperature changes in the air conditioned by said units for regulating the rate at which water is supplied to said units, of a master control apparatus for controlling the supply of water to all of said units irrespective of the operation of said individual control members and said temperature responsive member.

2. A control member for air conditioning apparatus and the like, including a humid- -ity-responsive member comprising a sinusoidally arranged, thin fabricated strip of hygroscopic material, an electric switch,

and connections between said switch and said humidity-responsive member whereby the switch will be operated in response to changes in humidity conditions of the surrounding atmosphere.

3. 'A control member for air conditioning apparatus and the like, including a humidity-responsive member and an electric switch mechanism actuated thereby, said humidity-responsive member including a strip of hygroscopic material, a pair of similar roller-carrying bearing members upon the rollers of which said strip is suspended in sinusoidal arrangement, a suspension member to which one of said bearing members is connected, and a lever-arm provided with means to which the other bearing member is connected, said lever-arm forming a part of said switch mechanism, said connec- 'tions serving to suspend said strip under tension whereby its contraction and extension in response to changes in humidity conditions will be effective to operate said switch.

4. A control member for air conditioning apparatus and the like, including a humidity-responsive member and an electric switch mechanism actuated thereby, -said humidity-responsive member including a strip of hygroscopic material, a pair of similar roller-carrying bearing members upon the rollers of which said strip is suspended in sinusoidal arrangement, a suspension member to which one of said hearing members is connected, a lever-arm provided with means to which the other bearing member is connected, said lever-arm forming a part of said switch mechanism, said connections serving to suspend said strip under tension whereby its contraction and extension in response to changes in humidity conditions will be effective to operate said switch, and means cooperating with said suspension member for adjusting the position of said suspension member.

5. A control member for air conditioning apparatus and the like, including a humidity-responsive member and an electric switch, said switch comprising a pair of stationary contacts, a swinging arm carrying contacts complemental to said stationary contacts, lever mechanism for imparting swinging movement to said arm, connections between said lever mechanism and said humidity-responsive member whereby movement may be imparted to said arm in response to changes in humidity conditions, and means associated with said arm for imparting a rapid and positive switching movement thereto when such movement has been initiated by said lever mechanism.

6. A control member for air conditioning apparatus and the like, including a humidity-responsive member comprising a reversely bent, thin fabricated strip of hygroscopic material, means for controlling a Ion humidifier and connecting means between said control means and said humidity responsive member whereby the control means will be operated in response to changes in humidity conditions of the surrounding atmosphere.

7. In apparatus for controlling air condi tioning apparatus, the combination with a humidifier, of means for controlling the supply of water to said humidifier, a hygro scopic element comprising a reversely bent, thin strip of hygroscopic material having its bends spaced from one another and means connecting said element to said control means.

8. The invention as set forth in claim 7 wherein said element comprises a foraminous casing surrounding said strip of hygroscopic material.

9. The invention as in claim 7, wherein said element comprises a pair of end frames, each having a plurality of rollers and said strip is wound over certainof said rollers.

10. A control unit for air conditioning apparatus comprising a bed-plate, an electric switch depending from said bed-plate, a hygroscopic member, means mounting said member above said bed-plate and means including a member extending through said bed-plate and connected to said hygroscopic member for operating said switc 11. The invention as set forth in claim 10, wherein said mounting means comprises an elongated member secured to saidbed-plate, and extending upwardly therefrom, a cross member resting on the top end of said elongated member andconnected to the upper end of said hygroscopic member and means for moving said elongated member axially of itself.

12. A control unit for air conditioningapparatus comprising a base, means mounted on said base for controlling a humidifier, a hygroscopic member, means including aleaf spring mounting said member on said base, and means including aleaf spring clamped to said hygroscopic member for operating said controlling means.

13. In a hygroscopm control device, the combination with relatively fixed and movable supports, of a hygroscopic element attached to said supports and operative to move said movable support as said element changes in length due to varying humidity, control means actuated by said movable support, and means yieldingly opposing movement of said movable support in a direction corresponding to a decrease in the length of said element, said element comprising a multiplicity of ribbon-like strands of hygroscopic material spaced apart to permit circulation of air about each individual strand.

14. The invention as set forth in claim 13, wherein said strands comprise paper, and the total cross-sectional area of said strands is such that the unit tensile stress established in said paper by said last-mentioned means is of an order of magnitude substantially lower than the elastic limit of the paper.

15. The invention as set forth in claim 13 wherein said multiplicity of strands is formed of a strip of hygroscopic material reversely bent upon itself at each of said supports.

16. The invention as set forth in claim 13, wherein a strip of paper is reversely bent to provide the said multiplicity of strands of hygroscopic material. v

17. A control unit for air conditioning apparatus comprising a bed-plate, an electric switch depending from said bed-plate, a hygroscopic member, means including a leaf spring mounting said member on said bed-plate, and means including a leaf spring connected to said member for operating said switch.

In testimony whereof, I aflix my signature.

FREDERIC F. BAHNSON. 

